This invention relates to E-I and E-E transformers.
The magnetic circuit of an E-I transformer commonly comprises a ferromagnetic E core, which has two outer legs and an inner leg, and a ferromagnetic yoke in the form of a straight bar, the E core and the yoke being so arranged that a doubly closed magnetic circuit is obtained.
The magnetic circuit of an E-E transformer commonly comprises a first ferromagnetic E core, which has two outer legs and an inner leg, and a second ferromagnetic E core, which is identical to the first E core and also has two outer legs and an inner leg, the two E cores being so arranged that a doubly closed magnetic circuit is obtained. The respective two outer legs then form two outer links, and the two inner legs form an inner link.
The aforementioned magnetic circuits become electric power transformers if at least two coils, each of which is placed on one of the outer legs or outer links, or one of which is placed on an outer leg or outer link and the other on the inner leg or inner link, or both of which are placed on an outer leg or outer link or on the inner leg or inner link, interact with the magnetic circuit.
Such transformers serve to provide isolation between primary and secondary circuits for, e.g., AC signals, DC/DC converters, etc. So far, a special transformer has been used for each of these applications.
It is an object of the invention to design E-I transformers and E-E transformers in such a manner that signals which are independent of each other can be transferred simultaneously, without the signals interfering with each other. To attain this object, a first variant of the invention consists in an E-I transformer comprising
a ferromagnetic E core, having a first and a second outer leg and an inner leg,
a ferromagnetic yoke in the form of a straight bar which is so arranged that it and the E core form a doubly closed magnetic circuit,
a first coil, wound around the inner leg,
a second coil, wound around the inner leg,
a third coil, wound around the first outer leg, and
a fourth coil, wound around the first outer leg.
To attain the above object, a second variant of the invention consists in an E-E transformer comprising
a first ferromagnetic E core, which has a first and a second outer leg and a first inner leg,
a second ferromagnetic E core, which is identical to the first E core, has a third and a fourth outer leg and a second inner leg, and is so arranged
that it and the first E core form a doubly closed magnetic circuit
which has a first outer link, a second outer link, and an inner link,
a first coil, wound around the inner link,
a second coil, wound around the inner link,
a third coil, wound around the first outer link, and
a fourth coil, wound around the first outer link.
In a first preferred embodiment of each of the two variants of the invention, the first coil is placed beside the second coil.
In a second preferred embodiment of the invention, which can also be used with the first preferred embodiment, the third coil is placed beside the fourth coil.
In a third preferred embodiment of the invention, which can also be used with the first and second preferred embodiments, the first coil and the second coil are, respectively, a primary coil and a secondary coil of a first AC power transmission path, and the third coil and the fourth coil are, respectively, a primary coil and a secondary coil of a second AC power transmission path.
According to a further development of the third preferred embodiment of the invention, the frequency of the first AC power is substantially less than the frequency of the second AC power, with the first coil and the second coil preferably being a primary coil and a secondary coil, respectively, of a DC/DC converter, and the third coil and the fourth coil serving to accomplish an electrically separated transfer of digital signals.
In another preferred embodiment of the invention, a transformer according to any one of the above-mentioned embodiments is used in a physical-to-electrical transducer with on-board evaluation electronics.
In a further preferred embodiment of the invention, the transformer is used in a physical-to-electrical transducer with on-board evaluation electronics, with the third coil having an external two-wire field bus connected thereto, and the fourth coil interacting with a digital circuit of the on-board evaluation electronics.
One advantage of the invention is that one and the same transformer can be used for two different functions, which saves material and space. The space saving is of particular importance if at the locations of the transformers, only little space is available for electronic components; that is frequently the case with industrial measuring devices, because the forms of their housings are generally standardized.